For the first time researchers from the U.S. and abroad have shown a single-dose HIV DNA vaccine can induce a long-lasting HIV-specific immune response in nonhuman primates, a discovery that could prove significant in the development of HIV vaccines. They detail their findings in the February 2010 issue of the Journal of Virology.

HIV is persistently spreading at epidemic rates throughout the world emphasizing the need for a vaccine that can substantially reduce viral loads and minimize transmission. History shows vaccines to be the most effective strategy against pandemic infectious diseases such as smallpox, polio, measles and yellow fever, however, the control of HIV not only relies on the production of neutralizing antibodies, but also the development of high frequency, broadly targeted T-cell responses specific to the virus. To date live-attenuated simian immunodeficiency virus (SIV)/HIV vaccines have prompted the most significant immune response against AIDS in a nonhuman primate model, but risk of redeveloping pathogenic forms makes them ineligible for human use.

DNA-based vaccines have become more preferable in controlling infectious diseases due to their safety and ability to induce both humoral and T-cell immune responses. In a previous study the researchers successfully induced long-lasting and potent HIV-specific immune responses in mice following immunization with a single-dose SHIV DNA-based vaccine. In this study rhesus macaques were immunized with a single high dose of the SHIV DNA-based vaccine and monitored for vaccine-induced immune responses. Results showed that all immunized monkeys developed broad HIV-specific T-cell immune responses that persisted for months. Additionally, an unusual reemergence in the blood following an initial decline and in the absence of antibody responses was noted.

"Our comprehensive analysis demonstrated for the first time the capacity of a single high dose of HIV DNA vaccine alone to induce long-lasting and polyfunctional T-cell responses in the nonhuman primate model, bringing new insights for the design of future HIV vaccines," say the researchers.